Opposing counsel in a six-year legal battle over a proposed Farmers Branch immigration ordinance are trading letters to the judge, arguing, naturally, that the U.S. Supreme Court's ruling on Arizona's immigration law supports their side.

Last month, the high court struck down the most controversial provisions of Arizona's law save one, which it left standing only conditionally. The remaining piece was one of the most controversial components of the law, allowing police to verify the immigration status of anyone they suspect is undocumented. The justices left the feds an opening for future lawsuits, saying the provision would remain constitutional only as long as suspected undocumented immigrants guilty of jaywalking, for example, aren't held by police performing an immigration check for longer than they otherwise would be.

Farmers Branch's ordinance, on the other hand, would require every tenant in a rental apartment or home to register with the town building inspector responsible for verifying their lawful immigration status. The ordinance's supporters and Farmers Branch's attorney, Kansas Secretary of State Kris Kobach, say the ordinance upholds federal immigration law. Apartment complex owners and documented and undocumented residents, represented by the ACLU and Dallas-based Bickel & Brewer Storefront, say Farmers Branch is stepping all over the feds' toes. A three-judge panel of the 5th U.S. Circuit Court of Appeals agreed and rejected the ordinance as an unconstitutional attempt to exclude undocumented immigrants, specifically Latinos, from Farmers Branch.

In a letter to the court last month, the ACLU said the Farmers Branch ordinance was akin to the invalidated provision of Arizona's law that required that undocumented immigrants register with the state. They claim it runs "contrary to the requirement of a national voice on immigration policy," as articulated by the Supreme Court.

Days later, Kobach responded, arguing that the high court upheld the part of the Arizona law that was most similar to the Farmers Branch law. Local authorities, he writes, have every right to communicate with the federal government. Kobach balked at the idea that Farmers Branch's registration requirement was trumped by federal law. Citizens, he reasoned, must register along with non-citizens.

On Friday, Bickel & Brewer Storefront responded with its own letter, dismissing Kobach's distinction. There's a big difference, William Brewer wrote, between asking the Feds for information and using that information to deny an alleged undocumented immigrant housing.

Farmers Branch is seeking a rehearing from the full panel of the 5th Circuit. Attorneys arguing against the ordinance say it should be denied.